Engineering substrate reduction and product oxidation in photocatalytic NADH synthesis via interface–pore co-confinement

In photocatalytic hydrogenation, non-directional transfer of electrons and indiscriminate oxidation of products by holes often result in severe electron–hole recombination and unintended product degradation, limiting overall efficiency. Herein, we engineer both the substrate reduction and product oxidation pathways through an interface–pore co-confinement strategy, exemplified by a rationally designed covalent organic framework (COF)-bridged core–shell photocatalyst (U@TpBpy-Rh) and photocatalytic NADH synthesis. The resultant U@TpBpy-Rh functions through dual mechanisms: (1) the confined S-scheme heterojunction interface facilitates directional electron transfer from MOF core to Rh sites in COF, significantly enhancing the photocatalytic NADH synthesis with productivity of 2.82 mmol g −1 h −1 ; (2) the confined pores of the COF shell restrict NADH diffusion toward highly oxidative MOF regions, reducing its oxidation degradation by 63% compared to U@TpBpy. This work demonstrates simultaneous spatiotemporal management of competitive photocatalytic reduction and oxidation pathways and will offer a general strategy for optimizing other redox-coupled reactions.